Fix race in spawning function-based actors
Fix race in spawning function-based actors

spawn_fwd did not forward pointers to actors correctly as instances of actor,
resulting in a possible race, i.e., the reference count could drop to zero
before the function-based actor was initialized.

nq-ebaratte/actor-framework,actor-framework/actor-framework,DavadDi/actor-framework,actor-framework/actor-framework,DavadDi/actor-framework,nq-ebaratte/actor-framework,nq-ebaratte/actor-framework,DavadDi/actor-framework,actor-framework/actor-framework,actor-framework/actor-framework,DavadDi/actor-framework,nq-ebaratte/actor-framework